Multilevel Micro Research Articles

Nanosecond Laser Fabrication of Novel Micro-/Nanostructured Metal Surfaces: A Dual-Functional Supersurface Combining Antireflectivity and Superhydrophobic Properties.

The research and applications in the field of micro/nano surface manufacturing are progressively shifting their focus toward multifunctional surfaces. In practical applications, objects often need to operate under demanding environmental conditions, and single-function surfaces have inherent limitations in terms of performance, adaptability, and longevity. In this paper, a micro-/nanolayered structural strategy with dual functions of ultrahigh antireflective properties and superhydrophobicity was created on the surface of titanium alloy by using nanosecond pulsed laser processing, and two structural modes of periodic honeycomb and lattice with controllable shapes were designed. In addition, the morphology and formation mechanism of multilevel micro-/nanostructures were investigated in depth, combining laser texturization and silanization of substrate microstructures. The effects of the micro-/nanostructured morphology on the reflection and wettability properties were evaluated with different pulse widths and lateral overlap index. This study also demonstrated that water droplets exhibit excellent bouncing and rolling behavior on superhydrophobic surfaces, further verifying the excellent hydrophobic properties of the prepared samples. Furthermore, in addressing the challenges of susceptibility to dust contamination and performance degradation in extreme environments associated with antireflective surfaces, a series of durability and mechanical stability tests were conducted on controllability periodic micro-/nanostructured surfaces. Successfully meeting this challenge will open up great potential and opportunities for significant improvements in equipment performance and stable operation under extreme operating conditions.

The multi-scale meso-mechanics model of viscoelastic dentin

Human dentin is a hierarchical material with multi-level micro-/nano-structures, consisting of tubule, perti-tubular dentin (PTD) and intertubular dentin (ITD) as the major constituents at microscale; and the PTD and ITD are further composed of collagen and hydroxyapatite (HAp) crystals with different volume fractions at nanoscale. In most cases, the HAp is considered as elastic while the collagen as viscoelastic material. It is of great significance to study the hierarchical structure and viscoelasticity of human dentin to understand the mechanical properties of dentin for further development of restorative materials. Based on this, this paper focuses on multiscale modeling of the elastic properties and dynamic viscoelastic response of dentin and establishes a bottom-up micromechanics model from nano-to macro-scale. In order to study the nanostructural effect on the viscoelastic behavior of hierarchical structures, the homogenization theories of random platelets composites (HTRPC) and the locally-exact homogenization theory (LEHT) are introduced for the homogenization of heterogeneous materials of microstructures at different levels. The HTRPC, based on Eshelby Inclusion theory, is used to predict the effective modulus of PTD and ITD. The LEHT is a method for homogenizing multiphase dentin characterized by repeated unit cells (RUCs). The resulting predictions are in very good agreement with several experimental data from the literature. In addition, the results of nanostructrual effect on dentin show that the viscoelasticity of dentin is majorly contributed by collagen and the HAp greatly provide the strength and hardness of dentin. Furthermore, the ageing effect on dentin's viscoelasticity is considered from the proposed multiscale micromechanics model. It is demonstrated that the ageing effect is much more influential in affecting the loss moduli of dentin than the storage.

Influence of the Structural-Phase State of a Copper Substrate upon Modification with Titanium Ions on the Thermal Cyclic Resistance of a Coating Based on Zr-Y-O

The results of investigation of the surface of a copper substrate modified with titanium ions are presented. The phase composition, the structure, and the morphology of the surface of the copper alloy modified by titanium ions have been investigated by X-ray, SEM, and TEM. It has been established that there are the intermetallic phases of the Cu-Ti equilibrium diagram in the surface layer during the treatment of copper by the titanium ions. A multilevel micro- and nanoporous structure is formed in the modified layer. It has been established that the structure-phase state and morphology of the surface layers of copper directly effects on the thermocycler resistance and adhesion of the Zr-Y-O coating. The thermocyclic resistance of the Zr-Y-O coating increases by an order of magnitude, the adhesion to the substrate is 2 times if the substrate surface is treated with titanium ions for 6 min.

One-level microstructure-arrayed hydrophobic surface with low surface adhesion and strong anti-wetting function

To achieve both a low surface adhesion function and a high anti-wetting function, it is generally necessary to introduce multi-level micro–nano-structures on a surface. However, this will bring the difficulty of preparation technology, and the functions will fail due to the fact that the nanostructures can easily be damaged. In this research, the surface adhesion and anti-wetting properties of several typically one-level microstructure-arrayed hydrophobic surfaces are analyzed with the dynamics theory, including a square pillar-arrayed three-dimensional microstructure, a conical table-arrayed microstructure, and square frustum-arrayed microstructure. It is found that the anti-adhesion performance and anti-wetting property cannot achieve the best performance simultaneously on the one-level microstructure arrayed surfaces. Either the critical pressure of anti-wetting is finite when the surface adhesion is the lowest, or both the anti-adhesion and anti-wetting capacities are finite. However, an interesting phenomenon is found in that the square frustum-arrayed surface can not only achieve an almost infinite anti-wetting capacity when the distance between neighboring microstructures vanishes, but also reach near-zero adhesion when the square frustum reduces to a square pyramid. All the theoretical predictions are further verified by precise numerical simulations. The results of this paper should be helpful for the design of surfaces with low surface adhesion and strong anti-wetting functions in practical engineering.

EDTA interfacial chelation Ca2+ incorporates superhydrophobic coating for scaling inhibition of CaCO3 in petroleum industry

In this paper, the superhydrophobic poly(vinylidene fluoride)/fluorinated ethylene propylene/SiO2/CNTs-EDTA (PFSC-EDTA) composite coating was successfully fabricated and applied for anti-scaling performance. The deposition of CaCO3 on the surface of the superhydrophobic PFSC-EDTA composite coating reached 0.0444 mg/cm2 for 192-h immersion into the supersaturated CaCO3 solution, which was only 11.4% that of the superhydrophobic PFSC composite coating. At the interface between the CaCO3 solution and the PFSC-EDTA coating, the Ca2+ could be firstly chelated by EDTA that was benefit for improving the anti-scaling performance of the superhydrophobic PFSC-EDTA composite coating. In another hand, the addition of EDTA to the CNTs played an important role in fabricating the SiO2-centric and CNTs-EDTA-surrounded multilevel micro–nanostructure in the superhydrophobic PFSC-EDTA composite coating, in favor of maintaining the air film under the water and the stability of the superhydrophobic surface. The research supplies a new way of improving anti-scaling performance of superhydrophobic coating by incorporating the organic chelating agent at the interface and changing the traditional way of scale prevention.

Effect of Surface Modification of a Titanium Alloy by Copper Ions on the Structure and Properties of the Substrate-Coating Composition

To improve the strength properties, adhesion, and the thermal cycling resistance of ceramic coatings, the titanium alloy surface was modified with copper ions under different processing times. It is found that at the maximum processing time, the thickness of the alloyed layer reaches 12 μm. It is shown that the modified layer has a multiphase structure in addition to the main α and β–titanium phases with the intermetallic compounds of the Ti-Cu system. The parameters of the fine structure of the material are investigated by the X-ray diffraction analysis. It has been found that when the surface of the titanium alloy is modified, depletion occurs in the main alloying elements, such as aluminum and vanadium, the crystal lattice parameter increases, the root-mean-square (rms) displacements of the atoms decrease, and the macrostresses of compression arise. A multilevel micro- and nanoporous nanocrystalline structure occurs, which leads to an increase in the adhesion and the thermal cyclic resistance of the ceramic coating based on Si-Al-N.

RETRACTED ARTICLE: Protecting user profile based on attribute-based encryption using multilevel access security by restricting unauthorization in the cloud environment

Data security in centralized storage needs advancement in privacy standards because of all of the cloud. The data security in the cloud has been well provided by security industries like cloud network security, data center security, distributed security and soon, also their exist numerous techniques to preserve the privacy of cloud users. The earlier methods enforce user privacy by restricting the malicious access from various users. Data authentication is provable access to keep privacy among other standards. However, the privacy of cloud users has been breached on several occasions. To improve cloud security and enforce efficient privacy preservation, a multi-level micro access restriction algorithm has been presented in this paper. The cloud data has been indexed in multiple levels, the data present in each level has been restricted using the profile and set if encryption standards. The user request has been evaluated for its trusted access according to the access grant present in profile data. Similarly, the cloud data has been encrypted with the user key and the key belongs to the data owner. The method estimates micro access trust weight (MATW), which has been used to restrict the user from malicious access and to preserve user privacy. The method improves the performance of cloud security and introduces higher privacy preservation accuracy.

Study on Multi-level Microstructure of Plant Fiber

Compared with common artificial fibers, plant fibers have advantages of lower density, high strength, low cost, and they can be more easily extracted from plants. Thus, they are ideal reinforced materials to the development of high performance composite materials. Based on the existing research results of the applicant, we develop a kind of Hamiltonian system based boundary integral numerical model to analyse the micro mechanical properties of multi-level structure of plant fibers and its reinforced polymer composites. Using the microscopic observation and micro tensile test to determine the longitudinal mechanical parameters of plant fiber composite material and the lateral scale of the component materials, so that a multi-level micro mechanical model can be established.

Development of stacked conductive templates for electroforming of multi-level metallic micro components

Economic mass manufacturing of metallic micro components requires effective methods to produce the adequate partial conductive templates. Especially in case of stacked or multi-level micro components a considerable increase in economic efficiency could be achieved if originally made templates, e.g. by LIGA, would be replaced by much cheaper replicated ones. For this purpose a modified injection molding process to produce stacked and partially conductive polymeric templates had been developed. As suitable demonstrator a combination of a gear wheel with an adequate shaft was chosen. Electroforming trials using a standard nickel sulfamate electrolyte were carried out. Finally, the stepwise electroplating procedure filling the shaft cavity first subsequently the gear wheel cavity could be realized. The lateral dimensions were measured and the surfaces of the metal components were characterized by SEM.

Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability

Material surfaces with tailored aerophobicity are crucial for applications where gas bubble wettability has to be controlled, e.g., gas storage and transport, electrodes, bioreactors or medical devices.Here, we present switchable underwater aerophobicity of hydrophobic polymeric substrates, which respond to heat with multilevel micro- and nanotopographical changes. The cross-linked poly[ethylene-co-(vinyl acetate)] substrates possess arrays of microcylinders with a nanorough top surface. It is hypothesized that the specific micro-/nanotopography of the surface allows trapping of a water film at the micro interspace and in this way generates the aerophobic behavior. The structured substrates were programmed to a temporarily stable, nanoscale flat substrate showing aerophilic behavior. Upon heating, the topographical changes caused a switch in contact angle from aerophilic to aerophobic for approaching air bubbles. In this way, the initial adhesion of air bubbles to the programmed flat substrate could be turned into repellence for the recovered substrate surface. The temperature at which the repellence of air bubbles starts can be adjusted from 58 ± 3 °C to 73 ± 3 °C by varying the deformation temperature applied during the temperature-memory programming procedure. The presented actively switching polymeric substrates are attractive candidates for applications, where an on-demand gas bubble repellence is advantageous.

Hydrophobic/Hydrophilic Cooperative Janus Branched Polymer Fibers with Controllable Length and Density of Nanobranches

AbstractThe fabrication of a fiber with multilevel micro‐/nanostructures is still a great challenge. Here, a newly structured polymer fiber, which possesses both a hydrophobic/hydrophilic cooperative Janus stem and nanosized branches with controllable length and density, is developed via a microfluidic‐electrospinning technology for the first time. Both the length and density of the branches on the fiber can be controlled by changing the electrical conductivity of the inner phase of poly(vinyl alcohol) solution or the applied voltage. The mechanical analytic model reveals that when the coulomb force between surface charge of continuous phase and volume charge of dispersed phase, which is raised with the electrical conductivity of the inner phase or the applied voltage increasing, is greater than surface tension of continuous phase, the branches are formed; simultaneously, the Janus structure is generated through both the electrostatic repulsion and phase separation.

Research of lamellar lubricants mechanical-and-physical properties and structure

in the article ascertaining the applicability of lamellar solid lubricants is considered for the purpose of wear resistance increase of metal surface elements by their contact interaction in different operational conditions. Forms of binding in the structure of solid lubricants are described through the example of molybdenum disulfide MoS2, as well as change properties at standard and high (350-480°C) exposure temperature. After solid lubricant application the additional treatment is made on the work surface of flanged wheels in the wheel set of a locomotive using plastic deformation for getting of multilevel micro relief resulting in working service increase of the wheel set in comparison with control set from 1.6 to 3 times.

Micro structure processing on plastics by accelerated hydrogen molecular ions

A proton has 1836 times the mass of an electron and is the lightest nucleus to be used for accelerator in material modification. We can setup accelerator with the lowest acceleration voltage. It is preferable characteristics of Proton Beam Writer (PBW) for industrial applications. On the contrary “proton” has the lowest charge among all nuclei and the potential impact to material is lowest. The object of this research is to improve productivity of the PBW for industry application focusing on hydrogen molecular ions. These ions are generated in the same ion source by ionizing hydrogen molecule. There is no specific ion source requested and it is suitable for industrial use. We demonstrated three dimensional (3D) multilevel micro structures on polyester base FPC (Flexible Printed Circuits) using proton, H2+ and H3+. The reactivity of hydrogen molecular ions is much higher than that of proton and coincident with the level of expectation. We can apply this result to make micro devices of 3D multilevel structures on FPC.

Morphology evolution of poly(vinylidene fluoride) membranes during supercritical CO2 assisted phase inversion

A supercritical carbon dioxide (ScCO2) assisted phase inversion was developed to produce microporous poly(vinylidene fluoride) (PVDF) membranes whose morphology characteristics arise from both liquid-liquid demixing and solid-liquid demixing (crystallization). This result was confirmed by Fourier transform infrared spectroscopy (FTIR), from which both α and β crystals were found. As revealed by contact angle experiment, the PVDF membranes prepared via ScCO2 assisted phase inversion were more hydrophobic compared with the control membrane produced via conventional immersion-precipitation technique. In particular, the sample with 15 wt% PVDF prepared at 45 °C and 13 MPa exhibited a contact angle of 142°, which was mainly caused by the multilevel micro- and nano-structure. The effects of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and lithium chloride (LiCl) on the structures and crystal form were investigated. PVP promoted the formation of α phase crystal form, while PEG boosts the evolution of β phase. LiCl restrained the crystallization degree of PVDF membrane under ScCO2.

A semi-supervised hierarchical approach: two-dimensional clustering of microarray gene expression data

Micro array technologies have become a widespread research technique for biomedical researchers to assess tens of thousands of gene expression values simultaneously in a single experiment. Micro array data analysis for biological discovery requires computational tools. In this research a novel two-dimensional hierarchical clustering is presented. From the review, it is evident that the previous research works have used clustering which have been applied in gene expression data to create only one cluster for a gene that leads to biological complexity. This is mainly because of the nature of proteins and their interactions. Since proteins normally interact with different groups of proteins in order to serve different biological roles, the genes that produce these proteins are therefore expected to co express with more than one group of genes. This constructs that in micro array gene expression data, a gene may makes its presence in more than one cluster. In this research, multi-level micro array clustering, performed in two dimensions by the proposed two-dimensional hierarchical clustering technique can be used to represent the existence of genes in one or more clusters consistent with the nature of the gene and its attributes and prevent biological complexities.

1005 多段階インプリントプロセスによるセラミックシート表面上への多階層微細パターニング(生産加工・工作機械1)

1005 多段階インプリントプロセスによるセラミックシート表面上への多階層微細パターニング(生産加工・工作機械1)

Development of a cost-effective high-precision bench machine tool for multi-level micro aspheric lighting-lens mold machining

This study presents the development of a cost-effective high-precision bench machine tool prototype for machining multi-level micro aspheric lighting-lens molds. To achieve high-precision over a long lifetime of micromachining, the bench machine tool is designed using a small C-shaped framework to strengthen static rigidity and vibration resistance. The primary structures of the machine tool are constructed with tempered nodular graphite cast iron to obtain a high damping coefficient and high inherent resonant frequency. A multi-level aspheric curve generator is designed according to the multi-level aspheric curve equation to easily create an aspheric curve and then rotated into an aspheric surface form with a symmetrical optical axis. The verifications of the designed bench machine tool’s functions were conducted by machining the micro aspheric lighting-lens molds using high-speed micro milling. Experimental results demonstrate that form accuracy and surface roughness for the micro aspheric lightinglens mold of Rt 2.937 μm and Ra equal to 0.032 μm respectively could be simultaneously achieved. The developed cost-effective bench machine tool can supply high-quality and fast machining in the fabrication of micro optoelectronic molds such as those used for micro aspheric lighting-lenses.

A coevolutionary framework for analysing a transition to a sustainable low carbon economy

This paper proposes a coevolutionary framework for analysing a transition to a sustainable low-carbon economy, based on the coevolution of ecosystems, technologies, institutions, business strategies and user practices, within a multi-level micro–meso–macro perspective. This builds on and develops previous coevolutionary analyses of long-term technological and industrial change, and recent renewed interest within ecological economics on coevolutionary approaches. Previous work has analysed how the coevolution of technologies and institutions has led to the lock-in of current high-carbon energy systems; and how the coevolution of physical and social technologies and business strategies has brought significant material and welfare benefits to the minority of the world's population living in industrialised countries. The coevolutionary framework proposed here may be used to undertake: (1) detailed empirical analyses at a micro–meso level of the challenges relating to the innovation and adoption of particularly low-carbon technologies; (2) as a framework for analysing the multi-level interaction of social and technological elements within potential transition pathways to a low carbon energy system; (3) to assess the implications for economic growth and prosperity of a transition to a low carbon economy; and (4) to assist in the development of more formal, multi-level evolutionary economic models.

Multi-level micro-/nanostructures of butterfly wings adapt at low temperature to water repellency

We show that micro-/nanostructure effects achieve water repellency of Morpho nestira butterfly wings under low temperature and changeable relative humidity. It is found that the multi-level micro-/nanostructures on wing scales effectively retard low-temperature-induced wetting, and achieve water repellency, accompanied with low adhesion under environmental humidity conditions. The mechanism of the extended water repellency is elucidated based on the micro-/nanostructure effect that can be adapted to low temperature and relative humidity. This finding offers an insight into micro-/nanostructures of butterfly wings, which helps to design novel interface materials to be applied in anti-frosting, anti-fogging and anti-icing projects.

Clinical outcomes and invasiveness of multilevel micro fenestration via a unilateral approach for lumbar spinal canal stenosis

Clinical outcomes and invasiveness of multilevel micro fenestration via a unilateral approach for lumbar spinal canal stenosis